Corneal endothelial cells in man decrease in numbers with age and are not replaced following injury. If the injury is severe, or if subsequent stress occurs, corneal edema and loss of transparency may occur. Recent studies of corneal endothelial regeneration in many species in our laboratories have shown that the endothelium of cat reacts to injury in a fashion most similar to that of man. Cat is therefore being used as a model in our studies. The overall objectives are: 1) to compare the effects of drugs, irrigating solutions, inflammation, and increased intraocular pressure on the ultrastructure and function of regenerated and normal endothelium of cat cornea; 2) to determine effects of Vitamin A, thyroid hormones, and insulin on endothelial regeneration; and 3) to characterize the metabolic changes in regenerated and cultured endothelium.